In general, a semiconductor device that drives a semiconductor switching element based on an input signal is provided with an input determination circuit that includes a comparator for determining an input signal voltage level. In addition, when a power switch capable of flowing a large current therethrough, which is represented by an insulated gate bipolar transistor (hereinafter, referred to as an IGBT), is driven, there is a case in which, since a minute resistance component in wiring and the like serving as a current path may not be ignored and, for example, the potential of a ground in the vicinity of the power switching element increases by the product obtained by multiplying the minute resistance by a large current, which sometimes causes a malfunction, the ground is used separately from a ground for signal transmission (see, for example, JP 5900149 B).
An input determination circuit disclosed in JP 5900149 B includes a comparator 102 that is connected between a DC input terminal 101 and a ground GND1 having a first reference potential G1 and is supplied with DC electric power, as illustrated in FIG. 6. The input determination circuit is configured to compare an input signal voltage Vin input from an ECU 103 with a reference signal voltage Vref by means of the comparator 102 to perform level determination. In the input determination circuit, the reference voltage Vref that is input to the comparator 102 is output from the connection point between a constant current circuit 105 and a resistor 106 that are connected between the DC input terminal 101 and a ground GND2 having a second reference potential G2 that is different from the first reference potential. In addition, a series circuit of a constant current circuit 107 and a P-channel MOSFET 108 is connected in parallel with the constant current circuit 105, and a determination signal Sj output from the comparator 102 is supplied to the gate of the P-channel MOSFET 108. The above configuration causes the input signal voltage Vin and the reference signal voltage Vref to be formed at an identical reference potential (the ground GND2), which enables the comparator 102 to perform input determination with high accuracy.